U.S. Pat. No. 5,516,472 (Laver), which is incorporated herein by reference in its entirety, discloses a cellulosic-plastic composite and a method of processing the composite into a finished product. The method disclosed in Laver consists of passing material through a die extruder system composed of a series of nested dies. Among the types of dies included in the system are an adapter die, a transition die, a stranding die, a molding die, and a setting die. Each type of die is a flat plate that contains a number of channels. The size, quantity, and shape of the channels are determined by each die's particular function.
The method of processing cellulosic plastic composites in Laver works well at moderate extrusion rates (approximately 600 lb/hr), with raw materials of uniform particle size and consistent quality (in terms of purity and the physical and chemical properties of the various raw materials), and for generating relatively small product sizes. However, when the extrusion rates increase beyond a moderate value, raw materials with non-uniform particle size or general lower quality are used, or the extruded product is increased beyond a minimal size, defects appear in the extruded end product. The defects include a rough surface, unevenly dispersed ingredients, and decreased strength.